Killer of U.S. airmen is radical Muslim, German official says

NEW: Nicholas Alden, 25, a senior airman from South Carolina, was killed, the military says

The suspect left Kosovo at age 1 and was an ethnic Albania, a U.S. official says

Uka allegedly confessed and says he acted alone, a German intelligence official says

The suspect fired until his weapon jammed and then fled, a German official says

Frankfurt, Germany (CNN) -- The man who shot and killed two American troops in Germany was a recently radicalized Muslim who seems to have been influenced by local radical Islamist websites, a German official said Thursday.

Arid Uka told interrogators that his aim was to kill American troops, said Boris Rhein, interior minister of the German state of Hesse, where the shooting took place. Two U.S. airmen were killed and two others were wounded in the attack Wednesday on a U.S. military bus at Frankfurt Airport, authorities say.

The 21-year-old man said he was motivated to carry out the attack after seeing a video on the internet the day before, which he claimed showed American soldiers raping Muslim women, according to a German intelligence official who viewed a record of the suspect's interrogation.

The suspect confessed to the shooting, and said that he acted alone with no helpers, the German intelligence official told CNN on Thursday.

He was friends on Facebook with several pro-al Qaeda extremists from a group based in Bonn, Germany, that is known to German intelligence officials, according to the official. That included links to an Islamic preacher named Pierre Vogel and someone named Nessery, who was arrested about two months ago in Afghanistan, according to a U.S. official with direct knowledge of the investigation.

Current indications are that the suspect radicalized quickly, the German official said.

The gunman was a postal worker at the airport, but worked outside the secure area. The U.S. official said that Uka didn't appear to punch into work Wednesday -- having apparently canvassed the area beforehand, helping him get around the extensive uniformed and plain-clothes security that typically patrol the Frankfurt airport.

Another U.S. official on Thursday said that Uka was "not on the radar screen" of American authorities prior to the attack.

The suspect is from the northern town of Mitrovica, Kosovo's interior minister, Bajram Rexhepi, told CNN, citing the U.S. Embassy in Pristina as his source.

The U.S. official with knowledge of the probe said Uka was a 1-year-old toddler when he moved to Germany, and that authorities believe Uka's relatives had suffered in the 1990s during the Serb crackdown on ethnic Albanians.

He has passports from both Germany and Yugoslavia, the latter of which was issued prior to Kosovo's declaration of independence from Serbia in 2008, Rexhepi said.

Uka told interrogators that he lived with his family in high-rise public housing in a poor area of Frankfurt, the German intelligence official said. He said he did not have a friendly relationship with people in the neighborhood and did not interact with others there. He said his father was very strict and harsh with him, according to the official.

On Wednesday, he allegedly approached a bus, which was parked outside Terminal 2 and was clearly marked as a U.S. military vehicle, German police said after the shooting.

According to a U.S. official, the suspect approached one troop on the curb outside and asked him for a cigarette, only to be rebuffed. He then boarded the vehicle and shot over several rows of backpacks and luggage at troops in the back of the bus.

At some point the weapon jammed and the suspect fled, the German official said. He made it into the terminal, where he was taken into custody by German federal police, according to police.

The weapon was a 9 mm handgun that was illegally purchased, Rhein said.

The bus was occupied by 15 members of the security forces team that was on its way to Ramstein Air Force Base in Germany before deploying to Afghanistan, the spokesman said.

One of the dead airmen was a vehicle operator at Ramstein, and the second was part of a security forces team based in the U.K., an Air Force spokesman said.

Zachary Cuddeback was one of those killed, his grandfather, Daniel Cuddeback, told CNN. It's not clear if he was the vehicle operator or the member of the security forces team. A statement from his family described Cuddeback as a hockey player and "Army brat" with especially strong roots in Missouri in Virginia who joined the Air Force in 2009 after a year at Old Dominion University.

The U.S. Defense Department on Thursday identified the other victim as Senior Airman Nicholas J. Alden, 25, of Williamston, South Carolina. He had been assigned to the 48th Security Forces Squadron based out of the Lakenheath air base in Great Britain.

The two wounded troops were in a Frankfurt hospital, one in critical condition and the other in serious condition, an Air Force spokesman said.

These two were security forces who were on their way to a deployment, said a source, who did not want to be identified because he was not authorized to speak publicly about the incident.

U.S. President Barack Obama told reporters Wednesday he was "saddened and outraged" by the attack. "We will spare no effort in learning how this outrageous attack took place," he said.

German Chancellor Angela Merkel said how upset she was by the incident, expressed her condolences to the troops' families and stressed that Germany will "do everything we can to try and find out quickly what happened."

FBI agents were on the scene shortly after the shooting occurred, said Tom Fuentes, a former FBI assistant director and CNN contributor.

The FBI's main office in Germany is in the capital Berlin, he said, but it has a sub-office in Frankfurt.

The offense is a federal crime both in the United States and in Germany, he said, and could be prosecuted in either location, although that will be determined later. However, the investigation will meet U.S. constitutional standards, he said.